The subject matter disclosed herein relates generally to magnetic resonance imaging systems and, more particularly, to managing specific absorption rates into patients scanned by magnetic resonance imaging systems.
Magnetic resonance imaging (MRI) systems enable imaging based on a primary magnetic field, a radio frequency (RF) pulse, and time-varying magnetic gradient fields that interact with specific nuclear components in an object, such as hydrogen nuclei in water molecules. The magnetic moments of such nuclear components may attempt to align with the primary magnetic field, but subsequently precess at a characteristic frequency known as the Larmor frequency. An RF pulse at or near the Larmor frequency of such nuclear components may cause the magnetic moments to be rotated. When the RF pulse has ended, the magnetic moments may attempt to realign with the primary magnetic field, emitting a detectable signal.
Such electromagnetic signals may penetrate the object being scanned by an MRI scanner, which is typically a human patient, and deposit thermal energy into the object. The scanner may control the electromagnetic signals so as to limit a specific absorption rate (SAR) of energy into the object. However, current techniques for controlling the electromagnetic signals to a particular SAR may be relatively inexact, and may not account for differences in electrical properties among various objects that may be scanned by the scanner.